Messier 51 - The Whirlpool Galaxy in HaLRGB
Date: June 9, 2021
Cosgrove’s Cosmos Catalog ➤#0072
Messier 51 - The Whirlpool Galaxy (click image for full resolution via Astrobin.com)
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About the Target
Messier 51, also know as NGC 5194 is more famously known as the Whirlpool Galaxy. It can be found in the constellation Canes Venatici and is estimated to be about 31 Million Light Years from Earth. M51 was the first galaxy to be classified as having a Spiral and is know o have a Seyfert 2 active galactic core.
Wikipedia provides some more background:
“What later became known as the Whirlpool Galaxy was discovered on October 13, 1773, by Charles Messier while hunting for objects that could confuse comet hunters, and was designated in Messier's catalogue as M51.[ Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain, although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845, William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m) reflecting telescope at Birr Castle, Ireland, found that the Whirlpool possessed a spiral structure, the first "nebula" to be known to have one.[ These "spiral nebulae" were not recognized as galaxies until Edwin Hubble was able to observe Cepheid variables in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies even though they are seen close together.”
I always thought this galaxy had a pretty cool history - it really helped us to understand the scope of the known universe….
The Annotated Image
An annotated image of M51 created by using Pixinsight’s ImageSolver and AnnotateImage Scripts.
The Location in the Sky
IAU/Sky & Telescope Constellation Man of Canes Venatici - with M51 marked by the yellow arrow.
About the Project
Fortunately, we had three "clear" nights around the new moon this month. I say "Clear" because the skies had no clouds, but it was hot and humid and the sky transparency was not at all great! But if you have no clouds and no moon - you collect photons!
This time of year is a little tough in that the nights are also mighty short. I really could not start capture until 11 pm and I had to shut down shortly after 3 am.
This clearly reduces productivity!
On the other hand, I recently got my portable Astrophoto rig up and running, so I had 3 platforms capturing 3 targets at the same time! That's a first for me!
Three times the capture! (or… three times the likelihood of really screwing things up!)
This is the first image to come from that session. This was shot with my Astro-Physics 130mm OTA sporting an ASI2600MM-Pro camera and this is the second target have tried with that combination.
My first attempt at capturing M51 was done almost one year ago with an OSC camera and I captured about 70 minutes of data.
This time around I was able to capture on the nights of June 4th, 5th, and 6th and ended up with just short of 10 hours of data.
I collected Luminance and RGB data, but I also collected some shots through my narrowband Ha filter. I then created two versions of this image. In this version, folded in the Ha data - which provides the red blobs and highlight along with the spiral structure of the Galaxy. These are regions of intense new star formation.
I'm reasonably happy with the result - the Ha filter data lends some better structure to the arms of the galaxy and the mistiness of the companion galaxy looks to me like a big thumbs-up emoticon!
I also created a version without the Ha data, and I will post that one too, in case you are curious.
Which one do you like better?
I continue to be impressed with this new camera - however, I did find that the 2600 cooler could not handle the hotter weather and could not get down to -15C as I desired. (note my two other ASI1600MM-Pros) had no trouble doing this). I assume the larger format APC-C sensor just generates that much more heat when operating. So I ended up running them at -10C.
Comparison to Previous Imaging Efforts
This is the third time that I have imaged M51. I originally imaged this in 2019 right after I had my first telescope up platform up and running. I captured it again a year ago in 2020.
M51 2019 version - Click HERE
M51 2020 version - Click HERE.
Here are the three images side-by-side (Click on the image to zoom in):
M51 - Initial 2019 OSC Version
M51 - 2020 OSC Version
M51 - 2021 Mono Version - HaLRGB
The first two versions were taken with the same basic rig - so the differences are due to integration time, better methodology, and better processing. The last version is on a different scope platform and a new “next-generation” mono camera. So the rig allows for some improvements and well some advanced processing ( i.e folding Ha data into the mix. )
More Information
Wikipedia: Messier 51
HubbleSite.org: "X" STRUCTURE AT CORE OF WHIRLPOOL GALAXY (M51)
Capture Details
Light frames
Number of frames is after bad or questionable frames were culled.
67 x 90 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II L Filter
77 x 90 seconds, bin 1x1 @ -15C, 0 gain, ZWO Gen II R Filter
63 x 90 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II G Filter
62 x 90 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II B Filter
11 x 300 seconds, bin 1x1 @ -15C, unity gain, Astronomiks 6nm Ha Filter
Total of 9.9 hours
Cal Frames
30 Darks at 300 seconds, bin 1x1, -10C, gain 100
30 Darks at 90 seconds, bin 1x1, -10C, gain 0
30 Dark Flats at Flat exposure times, bin 1x1, -15C, gain 0
Flats done separately for each evening to account for camera rotator variances:
30 L Flats
30 R Flats
30 G Flats
30 B Flats
30 Ha Flats
Capture Hardware
Scope: Astrophysics 130mm Starfire F/8.35 APO refractor
Guide Scope: Televue 76mm Doublet
Camera: ZWO AS2600mm-pro with ZWO 7x36 Filter wheel with ZWO LRGB filter set,
and Astronomiks 6nm Narrowband filter set
Guide Camera: ZWO ASI290Mini
Focus Motor: Pegasus Astro Focus Cube 2
Camera Rotator: Pegasus Astro Falcon
Mount: Ioptron CEM60
Polar Alignment: Polemaster camera
Software
Capture Software: PHD2 Guider, Sequence Generator Pro controller
Image Processing: Pixinsight, Photoshop - assisted by Coffee, extensive processing indecision and second-guessing, editor regret and much swearing….
Adding the next generation ZWO ASI2600MM-Pro camera and ZWO EFW 7x36 II EFW to the platform…